Parametric Study on Electric Field-Induced Micro-/Nanopatterns in Thin Polymer Films

Abstract

Electric field-induced micro-/nanopatterns in thin polymer films, sometimes referred as electrohydrodynamic patterning, is a promising technique to fabricate micro-/nanostructures. Extensive attention has been attracted because of its advantages in microcontact (easy demolding) and low cost. Although considerable work has been done on this technique, including both experimental and theoretical ones, there still appears a requirement for understanding the mechanism of electrohydrodynamic patterning. Thus, we systematically studied the effect of different parameters on electrohydrodynamic patterning with a numerical phase field model. Previous researchers usually employed lubrication approximation (i.e., long-wave approximation) to simplify the numerical model. However, this approximation would lose its validity if the structure height is on the same scale or larger than the wavelength, which occurs in most cases. Thus, we abandoned the lubrication approximation and solved the full governing equations for fluid flow and electric field. In this model, the deformation of polymer film is described by the phase field model. As to the electric field, the leaky dielectric model is adopted in which both electrical permittivity and conductivity are considered. The fluid flow together with electric field is coupled together in the framework of phase field. By this model, the effect of physical parameters, such as external voltage, template structure height, and polymer conductivity, is studied in detail. After that, the governing equations are nondimesionalized to analyze the relationship between different parameters. A dimensionless parameter, electrical Reynolds number E, is defined, for which, a large value would simplify the electric field to perfect dielectric model and a small value leads it to steady leaky model. These findings and results may enhance our understanding of electrohydrodynamic patterning and may be a meaningful guide for experiments.

The Impact of the Electric Field on Surface Condensation of Water Vapor: Insight from Molecular Dynamics Simulation

“…Since water molecules are polar, an external electric field has a significant effect on the properties of water. Thus, electric fields have a wide range of industrial applications, such as electrospinning [34,35] and micro/nano-patterning [36]. Some simulations and experimental studies have been conducted to analyze the effect of an electric field on water characteristics.…”

Polarization Effect and Improvement of the Electroinduced Formation Efficiency of a Highly Viscous Liquid Bridge

“…For example, He et al 12 established the model considering gravity, viscosity, and surface tension and pointed out that viscosity can significantly affect the growth of a liquid surface. Song et al 13 used the leaky dielectric model to simulate the structural process of the liquid surface and showed that the increase of electric field intensity can effectively shorten the rise time of the liquid surface. Goldberg-Oppenheimer et al 14 and Itoh et al 15 suggested that the structural forming times can be reduced by reducing viscosity and increasing voltage, respectively.…”

Parametric scheme for rapid nanopattern replication via electrohydrodynamic instability

“…15 With regard to overcoming the limitations of spontaneous instability mediated by interfacial disjoining pressure and high cost of state-of-the-art lithographic techniques, electrohydrodynamic (EHD)-driven patterning, a novel bottom-up pattern fabrication using the electric eld-mediated instability, has drawn substantial attention ever since the pioneering work by Steiner's group. 17 EHD instability (i.e., electric eld-mediated instability) is not merely exploited for pattern transfer in a single-step, noncontact, versatile, and scalable manner, [18][19][20][21][22][23][24] but also provide diverse opportunities for nely tailoring the structural property by carefully selecting process parameters. [25][26][27][28][29][30][31] EHD-driven patterning is based on the phase instability behavior of a thin liquid lm under an applied out-of-plane electric eld that induces undulation of the liquid lm surface to form small patterns; this has been demonstrated experimentally via the fabrication of micro and nanoscale patterns.…”